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Re: [spf-discuss] Re: PermError: Too many DNS lookups at Microsoft.com

2006-05-07 07:54:39
On Sat, 6 May 2006 23:53:59 -0400 "Hector Santos" 
<spf-discuss(_at_)winserver(_dot_)com> wrote:

----- Original Message -----
From: "Julian Mehnle" <julian(_at_)mehnle(_dot_)net>

Hector Santos wrote:
Too bad I was out of the loop when this decision was made.

Thats a major difference in SPF implementations and now you see the
effect for large SPF organization/networks wishing to support SPF.

It was also a major security hole in the old SPF specification that 
needed
to be fixed.

I don't disagree with the need for a fix. I disagree with the low ball SWAG
of 10 limit for lookup mechanisms.   It is too low IMO and I would venture 
a
PERMERROR is premature for many older SPF large organizations records.  For
all intent and purpose it places an artificial limit on the total domains
(10) a large site may use.

No it doesn't.  It says that beyond a certain level of complexity the 
outbound network needs to be described in terms of IP addresses or using 
exists:.   

I'd encourage you to go back and review the archives.  While 10 was arrived 
at emperically based on list consensus, there is more to it than a swag.  

There are ways to deal with this.  As an example, query the a records for 
relay.pair.com.  That's one mechanism that covers several physical boxes.  
Julian already mentioned exists:.  The limits can be worked within.  Now 
that the RFC is out, both records and SPF libraries need to be updated to 
conform to it.

Again:

   Classic SPF(Microsoft) = SoftFail
   Current SPF(Microsoft) = PermError

Yes.  They need to update.

It has nothing to do with a interoperability issue but a "human SWAG"
artificial limit.  Again, this is not a recursive issue where there was a
real security hole concern.

No, it was a DOS concern.  Please see the list archives.

I would think, that if I was in the loop when this was being decided, I
would suggested that the end result should be the same.  If other words, if
the complete exhausted result is a SOFTFAIL, then the cut off would be a
SOFTFAIL as well.

This gets into how one deals with an error (not is there an error).  That's 
a matter of receiver policy and a good topic for a BCP type document.

Anyway, what's written is written.  I would love to see what Microsoft has
to say or what they end up correcting it with.  Scott, have you contacted
them yet?


No, but I will.

Scott K

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